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One of the side effects of lung irradiation is radiation pneumonitis, which can be manifested as dyspnea. However, dyspnea can be one of the presenting symptoms of cardiac disease and might cause confusion in diagnosis following lung irradiation. The purpose of this study was to evaluate the association between heart and lung doses, tumor location, with the development of heart/lung toxicity following irradiation.

Materials and Methods

Between 1991 and 2001, 215 patients were enrolled in a prospective clinical study to define predictors of RT-induced lung toxicity

All included patients had at least 6 months of follow up

Patients with dyspnea secondary to progression of intra-thoracic tumor <6months following XRT were excluded

CT-based 3D external beam radiation was used and the heart was contoured from the inferior pulmonary artery down to the diaphragm

Doses received by non-involved lung tissue and the heart were calculated

The ratio of MHD and MLD can be correlated with the incidence of heart and/or lung toxicities

Further analysis of doses to different heart chambers currently underway

Clinical/Scientific Implications

This paper addresses one of the very common problems seen in patients who are status post lung irradiation. In patients presenting with dyspnea, it is difficult in certain cases to separate lung from heart etiologies. This study has looked at the MHD received from radiation and has found no correlation with dyspnea, although there is a correlation between MHD and heart toxicities such as pericarditis, myocardial infarction. As such, RT-induced toxicity is more likely to present with symptoms other than dyspnea according to this study. This study did not look at patient hemoglobin levels to evaluate for any correlations. Previous mouse/rat studies have shown a higher incidence of radiation pneumonitis after irradiation to lower lobe tumors. This has also been shown in human studies. What is unclear is why this is the case. Is this due to an intrinsic higher sensitivity of the basal lung to radiation or is it because the lower lobes are larger and more relied upon for respiration? Further studies are needed to clarify this issue. In the mean time, all patients should undergo a complete clinical/laboratory work-up if there is any doubt regarding the etiology of their dyspnea following lung irradiation.

Feb 1, 2015 - The deep inspiration breath-hold technique is associated with a reduction in the mean heart radiation dose during left breast irradiation, according to a review published online Jan. 7 in the Journal of Medical Radiation Sciences.